| Message ID | 20221027112127.2433605-1-zengheng4@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] cifs: fix use-after-free caused by invalid pointer `hostname` | expand |
Zeng Heng <zengheng4@huawei.com> writes: > `hostname` needs to be set as null-pointer after free in > `cifs_put_tcp_session` function, or when `cifsd` thread attempts > to resolve hostname and reconnect the host, the thread would deref > the invalid pointer. > > Here is one of practical backtrace examples as reference: > > Task 477 > --------------------------- > do_mount > path_mount > do_new_mount > vfs_get_tree > smb3_get_tree > smb3_get_tree_common > cifs_smb3_do_mount > cifs_mount > mount_put_conns > cifs_put_tcp_session > --> kfree(server->hostname) > > cifsd > --------------------------- > kthread > cifs_demultiplex_thread > cifs_reconnect > reconn_set_ipaddr_from_hostname > --> if (!server->hostname) > --> if (server->hostname[0] == '\0') // !! UAF fault here > > CIFS: VFS: cifs_mount failed w/return code = -112 > mount error(112): Host is down > BUG: KASAN: use-after-free in reconn_set_ipaddr_from_hostname+0x2ba/0x310 > Read of size 1 at addr ffff888108f35380 by task cifsd/480 > CPU: 2 PID: 480 Comm: cifsd Not tainted 6.1.0-rc2-00106-gf705792f89dd-dirty #25 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > Call Trace: > <TASK> > dump_stack_lvl+0x68/0x85 > print_report+0x16c/0x4a3 > kasan_report+0x95/0x190 > reconn_set_ipaddr_from_hostname+0x2ba/0x310 > __cifs_reconnect.part.0+0x241/0x800 > cifs_reconnect+0x65f/0xb60 > cifs_demultiplex_thread+0x1570/0x2570 > kthread+0x2c5/0x380 > ret_from_fork+0x22/0x30 > </TASK> > Allocated by task 477: > kasan_save_stack+0x1e/0x40 > kasan_set_track+0x21/0x30 > __kasan_kmalloc+0x7e/0x90 > __kmalloc_node_track_caller+0x52/0x1b0 > kstrdup+0x3b/0x70 > cifs_get_tcp_session+0xbc/0x19b0 > mount_get_conns+0xa9/0x10c0 > cifs_mount+0xdf/0x1970 > cifs_smb3_do_mount+0x295/0x1660 > smb3_get_tree+0x352/0x5e0 > vfs_get_tree+0x8e/0x2e0 > path_mount+0xf8c/0x1990 > do_mount+0xee/0x110 > __x64_sys_mount+0x14b/0x1f0 > do_syscall_64+0x3b/0x90 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > Freed by task 477: > kasan_save_stack+0x1e/0x40 > kasan_set_track+0x21/0x30 > kasan_save_free_info+0x2a/0x50 > __kasan_slab_free+0x10a/0x190 > __kmem_cache_free+0xca/0x3f0 > cifs_put_tcp_session+0x30c/0x450 > cifs_mount+0xf95/0x1970 > cifs_smb3_do_mount+0x295/0x1660 > smb3_get_tree+0x352/0x5e0 > vfs_get_tree+0x8e/0x2e0 > path_mount+0xf8c/0x1990 > do_mount+0xee/0x110 > __x64_sys_mount+0x14b/0x1f0 > do_syscall_64+0x3b/0x90 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > The buggy address belongs to the object at ffff888108f35380 > which belongs to the cache kmalloc-16 of size 16 > The buggy address is located 0 bytes inside of > 16-byte region [ffff888108f35380, ffff888108f35390) > The buggy address belongs to the physical page: > page:00000000333f8e58 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888108f350e0 pfn:0x108f35 > flags: 0x200000000000200(slab|node=0|zone=2) > raw: 0200000000000200 0000000000000000 dead000000000122 ffff8881000423c0 > raw: ffff888108f350e0 000000008080007a 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > Memory state around the buggy address: > ffff888108f35280: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc > ffff888108f35300: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc >>ffff888108f35380: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc > ^ > ffff888108f35400: fa fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff888108f35480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > Fixes: 28eb24ff75c5 ("cifs: Always resolve hostname before reconnecting") > Signed-off-by: Zeng Heng <zengheng4@huawei.com> > --- > fs/cifs/connect.c | 1 + > 1 file changed, 1 insertion(+) Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index ffb291579bb9..1cc47dd3b4d6 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -1584,6 +1584,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) server->session_key.response = NULL; server->session_key.len = 0; kfree(server->hostname); + server->hostname = NULL; task = xchg(&server->tsk, NULL); if (task)
`hostname` needs to be set as null-pointer after free in `cifs_put_tcp_session` function, or when `cifsd` thread attempts to resolve hostname and reconnect the host, the thread would deref the invalid pointer. Here is one of practical backtrace examples as reference: Task 477 --------------------------- do_mount path_mount do_new_mount vfs_get_tree smb3_get_tree smb3_get_tree_common cifs_smb3_do_mount cifs_mount mount_put_conns cifs_put_tcp_session --> kfree(server->hostname) cifsd --------------------------- kthread cifs_demultiplex_thread cifs_reconnect reconn_set_ipaddr_from_hostname --> if (!server->hostname) --> if (server->hostname[0] == '\0') // !! UAF fault here CIFS: VFS: cifs_mount failed w/return code = -112 mount error(112): Host is down BUG: KASAN: use-after-free in reconn_set_ipaddr_from_hostname+0x2ba/0x310 Read of size 1 at addr ffff888108f35380 by task cifsd/480 CPU: 2 PID: 480 Comm: cifsd Not tainted 6.1.0-rc2-00106-gf705792f89dd-dirty #25 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x68/0x85 print_report+0x16c/0x4a3 kasan_report+0x95/0x190 reconn_set_ipaddr_from_hostname+0x2ba/0x310 __cifs_reconnect.part.0+0x241/0x800 cifs_reconnect+0x65f/0xb60 cifs_demultiplex_thread+0x1570/0x2570 kthread+0x2c5/0x380 ret_from_fork+0x22/0x30 </TASK> Allocated by task 477: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_kmalloc+0x7e/0x90 __kmalloc_node_track_caller+0x52/0x1b0 kstrdup+0x3b/0x70 cifs_get_tcp_session+0xbc/0x19b0 mount_get_conns+0xa9/0x10c0 cifs_mount+0xdf/0x1970 cifs_smb3_do_mount+0x295/0x1660 smb3_get_tree+0x352/0x5e0 vfs_get_tree+0x8e/0x2e0 path_mount+0xf8c/0x1990 do_mount+0xee/0x110 __x64_sys_mount+0x14b/0x1f0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 477: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x50 __kasan_slab_free+0x10a/0x190 __kmem_cache_free+0xca/0x3f0 cifs_put_tcp_session+0x30c/0x450 cifs_mount+0xf95/0x1970 cifs_smb3_do_mount+0x295/0x1660 smb3_get_tree+0x352/0x5e0 vfs_get_tree+0x8e/0x2e0 path_mount+0xf8c/0x1990 do_mount+0xee/0x110 __x64_sys_mount+0x14b/0x1f0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd The buggy address belongs to the object at ffff888108f35380 which belongs to the cache kmalloc-16 of size 16 The buggy address is located 0 bytes inside of 16-byte region [ffff888108f35380, ffff888108f35390) The buggy address belongs to the physical page: page:00000000333f8e58 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888108f350e0 pfn:0x108f35 flags: 0x200000000000200(slab|node=0|zone=2) raw: 0200000000000200 0000000000000000 dead000000000122 ffff8881000423c0 raw: ffff888108f350e0 000000008080007a 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888108f35280: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc ffff888108f35300: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc >ffff888108f35380: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc ^ ffff888108f35400: fa fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888108f35480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Fixes: 28eb24ff75c5 ("cifs: Always resolve hostname before reconnecting") Signed-off-by: Zeng Heng <zengheng4@huawei.com> --- fs/cifs/connect.c | 1 + 1 file changed, 1 insertion(+)